Spindle motor and storage disk drive apparatus

ABSTRACT

A spindle motor includes a stator unit and a rotor unit supported to be rotatable with respect to the stator unit. The stator unit includes a stator, a base portion including a through hole, and a circuit board. The circuit board includes a connection portion to which a conductive wire from the stator is connected after passing through the through hole, and an extending portion arranged to extend from the connection portion. A lower surface of the base portion includes a recess portion arranged to accommodate the connection portion, and a groove portion arranged to extend from the recess portion to have the extending portion arranged therein. A bottom surface of the groove portion includes a protrusion portion arranged to protrude downwards.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spindle motor, and more specificallyto a storage disk drive apparatus provided with the spindle motor.

2. Description of the Related Art

Conventionally, a spindle motor for rotating a storage disk is installedwithin a housing of a storage disk drive apparatus such as a hard diskdrive or the like is known. In such a storage disk drive apparatus, aprinted circuit board is arranged outside the housing and used forcontrolling the power supplied to the spindle motor and the operation ofthe spindle motor. The printed circuit board is electrically connectedto the stator of the spindle motor accommodated within the housing. Insuch a spindle motor, a portion of the printed circuit board is arrangedin a recess portion formed on the lower surface of the housing in aneffort to reduce the thickness of the spindle motor and the storage diskdrive apparatus.

In such an arrangement, conductive wires of the stator are drawn fromthe recess portion to the lower surface of the housing through a holeformed through the housing. Then the conductive wires are led to thelower surface of the printed circuit board via a through hole of theprinted circuit board and are connected to electrodes provided on thelower surface of the printed circuit board.

A flexible printed circuit board is used as the printed circuit boardin, e.g., a disk drive apparatus disclosed in Japanese Patent Laid-openPublication No. 2001-67775. The flexible printed circuit board isattached to a housing with a stepped portion to extend along the lowersurface of the housing. In this disk drive apparatus, a guide hole,through which a coil line of a stator is drawn, is formed in a bottomwall portion of a bracket of a spindle motor that forms a portion of thehousing. A coil line insertion hole communicating with the guide hole isformed at the center of a land portion of the flexible printed circuitboard attached to the lower surface of the bracket. The coil line isdrawn to the outside through the guide hole and the coil line insertionhole and is soldered to the land portion. At this time, the coil lineinsertion hole is closed by a solder to seal off the housing, therebypreventing an external air from entering the housing.

In case of the disk drive apparatus disclosed in Japanese PatentLaid-open Publication No. 2001-67775, however, there is a possibilitythat the sealing reliability may deteriorate due to a time-dependentchange of the solder or other causes.

The flexible printed circuit board extends from the recess portion ofthe housing toward the external region thereof where the flexibleprinted circuit board is connected to other circuit boards. When sealingthe guide hole and the coil line insertion hole with a sealant, there isa need to keep the sealant from flowing out to the external region.

Also, in accordance with an increased reduction in a thickness of thedisk drive apparatus, there is a demand for a further reduction in athickness of a base plate. As mentioned above, a recess portion in whicha portion of the flexible printed circuit board is arranged is definedin a lower surface of the base plate. In addition, a variety of recessportions are defined in an upper surface of the base plate toaccommodate components of the motor. This, in combination with thereduced thickness of the base plate as a whole, results in some specificareas of the base plate becoming extremely thin. Such extremely thinareas may decrease the rigidity of the base plate so greatly as toinduce a vibration in the rest of the motor.

SUMMARY OF THE INVENTION

According to preferred embodiments of the present invention, there isprovided a spindle motor used, for example, with a storage disk driveapparatus, the spindle motor including a stator unit and a rotor unitsupported to be rotatable about a central axis with respect to thestator unit.

The stator unit includes a stator arranged around the central axis, abase portion, and a circuit board. The base portion is arranged on alower side of the rotor unit in a direction parallel or substantiallyparallel to the central axis. The base portion includes a through holepassing therethrough in the direction parallel or substantially parallelto the central axis. The circuit board is attached to a lower surface ofthe base portion. The circuit board includes a connection portion towhich a conductive wire from the stator is connected after passingthrough the through hole, and a strip-shaped extending portion arrangedto extend from the connection portion. The lower surface of the baseportion includes a recess portion arranged to accommodate the connectionportion, and a groove portion arranged to extend from the recess portionto have the extending portion arranged therein. A bottom surface of thegroove portion includes a protrusion portion arranged to protrudedownwards.

Thus, spindle motors according to preferred embodiments of the presentinvention are able to achieve improved rigidity in the base portion.

Other features, elements, steps, characteristics and advantages of thepresent invention will become more apparent from the following detaileddescription of preferred embodiments of the present invention withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view showing a storage disk drive apparatus inaccordance with a first preferred embodiment of the present invention,which view is taken along a plane containing the central axis of theapparatus.

FIG. 2 is a section view showing a spindle motor, which view is takenalong a plane containing the central axis of the motor.

FIG. 3 is an enlarged bottom view showing the portion of a stator unitaround the central axis.

FIG. 4 is a partial section view showing a base plate, which view istaken along line A-A in FIG. 3.

FIG. 5A is a partial section view showing a modified example of the baseportion of the spindle motor.

FIG. 5B is a partial section view showing a modified example of a grooveportion.

FIG. 6 is an enlarged bottom view showing the portion around the centralaxis in a spindle motor in accordance with a second preferred embodimentof the present invention.

FIG. 7 is an enlarged bottom view showing a recess portion and itsneighborhood.

FIG. 8A is an enlarged bottom view showing a recess portion and itsneighborhood.

FIG. 8B is an enlarged bottom view showing a recess portion and itsneighborhood.

FIG. 9 is an enlarged bottom view showing a recess portion and itsneighborhood in a modified example of the spindle motor.

FIG. 10 is a partial section view showing a base plate, which view istaken along line B-B in FIG. 9.

FIG. 11 is an enlarged bottom view showing a recess portion and itsneighborhood in another modified example of the spindle motor.

FIG. 12 is a partial section view showing a base plate, which view istaken along line C-C in FIG. 11.

FIG. 13 is a partial section view showing a base plate in a furthermodified example of the spindle motor.

FIG. 14 is a bottom view showing yet another modified example of thebase plate.

FIG. 15 is a diagram illustrating a central region.

FIG. 16 is a diagram illustrating the central region and a flexibleprinted circuit board.

FIG. 17 is a partial section view of the base plate.

FIG. 18 is a diagram illustrating the central region and the flexibleprinted circuit board.

FIG. 19 is a partial section view of the base plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, the terms “upper”, “lower”, “left” and“right” used in explaining the positional relationship and orientationof individual members are intended to designate the positionalrelationship and orientation in the drawings and not to designate thepositional relationship and orientation when built in an actual device.

FIG. 1 is a section view showing the internal construction of a storagedisk drive apparatus 60 provided with an electric spindle motor 1 inaccordance with a first preferred embodiment of the present invention.The storage disk drive apparatus 60 may be, e.g., a hard disk drive. Thestorage disk drive apparatus 60 includes a storage disk 62 arranged tostore information, an access unit 63 arranged to read and writeinformation from and on the storage disk 62, a spindle motor 1 arrangedto hold and rotate the storage disk 62 and a housing 61 arranged toaccommodate the storage disk 62, the spindle motor 1 and the access unit63 within an internal space 610 thereof.

As shown in FIG. 1, the housing 61 preferably includes a first housingmember 611 and a second housing member 612. The first housing member 611has a top portion with an opening and a bottom portion to which thespindle motor 1 and the access unit 63 are fixed. The second housingmember 612 defines the internal space 610 by covering the opening of thefirst housing member 611. In the storage disk drive apparatus 60, thesecond housing member 612 is bonded to the first housing member 611 todefine the housing 61. Dust is extremely rare in the internal space 610of the housing 61.

The storage disk 62 is mounted on the spindle motor 1 and fixed theretoby a clamp 621, for example. The access unit 63 includes a head 631arranged to gain access to the storage disk 62 and magnetically performreading or writing of information, an arm 632 arranged to support thehead 631 and a head moving mechanism 633 arranged to move the arm 632 sothat the head 631 can be moved with respect to the storage disk 62 andthe spindle motor 1. With this construction, the head 631 gains accessto a desired position on the storage disk 62 in a state that it remainsadjacent to the storage disk 62 under rotation, thus performing thetasks of reading and/or writing information.

FIG. 2 is a section view of the spindle motor 1 used in the storage diskdrive apparatus 60 to rotate the storage disk 62, which view is takenalong a plane containing a central axis J1. Although FIG. 2 shows thecross section taken along the plane containing the central axis J1 ofthe spindle motor 1, a portion of the component lying at the rear sideof the cross sectional plane is also illustrated by a broken line. Thecentral axis J1 coincides with the central axes of a stator unit 2 and arotor unit 3.

Referring to FIG. 2, the spindle motor 1 includes the stator unit 2 andthe rotor unit 3. The rotor unit 3 is supported by the stator unit 2 toenable rotation about the central axis J1 relative to the stator unit 2through a bearing mechanism that preferably makes use of a dynamic fluidpressure generated by lubricating oil as a lubricant.

The rotor unit 3 includes a generally disk-shaped rotor hub 31, agenerally cylindrical yoke 34, a rotor magnet 32, a shaft 33 and agenerally disk-shaped thrust plate 35. The storage disk 62 (see FIG. 1)is mounted to the rotor hub 31. The rotor hub 31 serves to holdindividual components of the rotor unit 3 in place. The yoke 34protrudes downwards form the outer circumferential edge of the rotor hub31. The rotor magnet 32 is fixed to the inner circumferential surface ofthe yoke 34 and is arranged around the central axis J1. The shaft 33 hasa generally columnar shape concentric with the central axis J1 andprotrudes downwards from the rotor hub 31. The thrust plate 35 is fixedto the lower end of the shaft 33. The rotor magnet 32 is magnetized withmultiple poles and is adapted to generate a rotational force (torque)acting about the central axis J1 between itself and a stator 24 of thestator unit 2.

The stator unit 2 includes a base plate 21, a sleeve unit 22, the stator24 and a thin flexible printed circuit board 25. The base plate 21defines a portion of the first housing member 611 (see FIG. 1) and holdsindividual components of the stator unit 2 in place. In the presentpreferred embodiment, the term “base portion” refers to the firsthousing member 611. The sleeve unit 22 is a portion of the bearingmechanism that rotatably supports the rotor unit 3. In the presentpreferred embodiment, the term “sleeve portion” refers to the sleeveunit 22. The stator 24 is fixed to the base plate 21 around the sleeveunit 22. The flexible printed circuit board 25 is attached to the lowersurface 211 of the base plate 21 and electrically connected to thestator 24. The flexible printed circuit board will be referred to as“FPC” below.

The sleeve unit 22 includes a generally cylindrical sleeve body 221, agenerally cylindrical sleeve housing 222 with a bottom portion, and agenerally cylindrical seal member 223. The shaft 33 is inserted into thesleeve body 221. The inner circumferential surface of the sleeve body221 opposes the outer circumferential surface of the shaft 33 through alubricant. The sleeve housing 222 is fixed to the outer circumferentialsurface of the sleeve body 221. The seal member 223 is arranged abovethe sleeve body 221. The sleeve body 221 is preferably made of a poroussintered metal, but could be made from any desirable material. Thesleeve housing 222 and the seal member 223 serve to hold the lubricantwith which the sleeve body 221 is impregnated. The lower portion of thesleeve unit 22 is press-fitted and fixed to the opening of the baseplate 21 arranged at the central region of the latter.

The stator 24 includes a stator core 241 having a plurality of teeth 243radially arranged about the central axis J1, and a plurality of coils242 formed by winding conductive wires on the teeth 243, for example.The conductive wires extending from the stator 24 are drawn out of thehousing 61 via through holes 212 and 250 respectively defined throughthe base plate 21 and the FPC 25 in parallel or substantially inparallel to the central axis J1. Then, the conductive wires are bonded,by a solder, to electrodes provided on the lower surface 251 of the FPC25. The FPC 25 is attached to the lower surface 211 of the base plate 21by an adhesive agent such as an adhesive or the like, for example. TheFPC 25 is partially covered with a resin layer 26. Examples of theadhesive agent include a pressure-sensitive adhesive (PSA).

FIG. 3 is an enlarged bottom view showing the portion of the stator unit2 around the central axis J1. In the following description, an annularregion 213 of the lower surface 211 of the base plate 21 concentric withthe central axis J1 as shown in FIG. 3 will be referred to as a “centralregion 213”. Furthermore, the region existing around the central region213 of the lower surface 211 of the base plate 21 will be referred to as“peripheral region 214”. As shown in FIG. 2, the peripheral region 214includes an annular slanting area 2141 and a horizontal area 2142perpendicular or substantially perpendicular to the central axis J1. Theslanting area 2141 lies radially outwardly of the central region 213 andcontinuously extends from the latter. The slanting area 2141 extendsgradually upwards as it extends away from the central axis J1. Thehorizontal area 2142 lies radially outwardly of the slanting area 2141and continuously extends from the latter.

As can be seen in FIG. 3, a recess portion 215 indented upwards inparallel or substantially in parallel to the central axis J1 is arrangedinwardly of the outer circumferential edge of the central region 213.When seen in a plan view, the recess portion 215 has a sector shapeconcentric with the central axis J1 but having no center-side region.This shape will be referred to as a sector shape herein below. Theperiphery of the recess portion 215 is surrounded by a raised portion2131 for most of its circumference. The borders between the radial innerand outer ends of the recess portion 215 and the raised portion 2131 aredefined into a generally arc-like shape concentric with the central axisJ1. A groove portion 216 extending radially outwardly from the recessportion 215 and interconnecting the recess portion 215 and theperipheral region 214 is arranged in the region of the raised portion2131 lying radially outwardly of the recess portion 215. The grooveportion 216 and the recess portion 215 communicate with each other.

As shown in FIG. 2, the bottom surface of the groove portion 216 issubstantially flush in an axial direction with the bottom surface of therecess portion 215. The slanting area 2141 and the horizontal area 2142of the peripheral region 214 are positioned higher than the grooveportion 216. Referring to FIG. 3, the width of the groove portion 216(namely, the width in a direction perpendicular or substantiallyperpendicular to the radial direction) is smaller than the width of therecess portion 215 and remains substantially constant in the radialdirection. Although not shown in FIG. 3, the opposite side surfaces ofthe groove portion 216 are preferably chamfered near the boundarybetween the recess portion 215 and the groove portion 216 and near theboundary between the groove portion 216 and the peripheral region 214.The width of the groove portion 216 near the boundaries is therefore alittle greater than the width of the groove portion 216 in the radialintermediate extension of the latter.

The raised portion 2131 has the shape of an annulus concentric with thecentral axis J1, a portion of which is removed along the circumferentialdirection (a so-called “partially annular shape”). This shape will bereferred to as a partially annular shape herein below.

The raised portion 2131 includes a partially annular portion 2132 andtwo generally arc-like arm portions 2133. The partially annular portion2132 surrounds the radial inner side and the circumferential oppositesides of the sector-shaped recess portion 215. The arm portions 2133protrude from the partially annular portion 2132 along the radial outerside of the recess portion 215 and surround the radial outer side of therecess portion 215 except the portion of radial outer side connected tothe groove portion 216. In the central region 213, the raised portion2131 is arranged into an arc-like shape to surround the recess portion215 at the circumferential opposite sides of the latter. The armportions 2133 prevent a flowable resin material from flowing out to theperipheral region 214 when the flowable resin material is applied on therecess portion 215 as will be set forth later. The arm portions 2133serve as a dam portion.

As described above, the lower surface 211 of the base plate 21positioned below the rotor unit 3 includes the central region 213, theperipheral region 214, the recess portion 215 and the groove portion216. When seen in a plan view, the central region 213 overlaps with thestator 24. The peripheral region 214 is arranged around the centralregion 213 and positioned higher than the central region 213. The recessportion 215 is arranged within the central region 213. The grooveportion 216 interconnects the recess portion 215 and the peripheralregion 214.

As shown in FIG. 3, the FPC 25 includes a connection portion 252, anexternal terminal portion 254 and a strip-shaped extending portion 253.The connection portion 252 has electrodes 255 to which the conductivewires extending from the stator 24 are connected. The external terminalportion 254 is provided with terminals arranged to connect with externaldevices, the terminals being used to connect the FPC 25 to other circuitboards (e.g., a circuit board arranged to drive and control the spindlemotor 1). The wiring lines extend from the electrodes 255 of theconnection portion 252 to the terminals of the external terminal portion254 along the extending portion 253. In the stator unit 2, as shown inFIGS. 2 and 3, the connection portion 252 of the FPC 25 is accommodatedwithin the recess portion 215 of the lower surface 211 of the base plate21, and the external terminal portion 254 is arranged in the slantingarea 2141 and the horizontal area 2142 of the peripheral region 214. Theextending portion 253 extending from the connection portion 252 of theFPC 25 to the peripheral region 214 is arranged within the grooveportion 216.

FIG. 4 is a section view of the base plate 21 taken along line A-A inFIG. 3. In FIG. 4, the base plate 21 is depicted in a verticallyinverted state so that the lower surface 211 of the base plate 21 can bepositioned at the upper side in the figure (this also holds true inFIGS. 5A, 5B, 10, 12 and 13). Referring to FIG. 4, the bottom surface2161 of the groove portion 216 in which the extending portion 253 of theFPC 25 is arranged is positioned higher, in the direction of the centralaxis J1, than the area of the central region 213 excluding the recessportion 215 (see FIG. 3) and the groove portion 216. The bottom surface2161 of the groove portion 216 is one of the surfaces of the grooveportion 216 positioned at the upper side. In FIG. 4, the bottom surface2161 is depicted as if it is positioned at the lower side of the grooveportion 216. The opposite side surfaces 2162 of the groove portion 216are inclined in a manner such that they gradually slope downwards asthey go away from the bottom surface 2161 in the circumferentialdirection. The opposite side surfaces 2162 refer to the surfaces thatextend from respective lateral sides of the bottom surface 2161 to thecorresponding lower edges 2168 of the groove portion 216 in thecircumferential direction about the central axis J1. The angle θ1between the bottom surface 2161 and the opposite side surfaces 2162 ofthe groove portion 216 is in a range of from approximately 95° toapproximately 175°.

In the groove portion 216, the extending portion 253 of the FPC 25attached to the bottom surface 2161 of the groove portion 216 is spacedapart from the opposite side surfaces 2162 of the groove portion 216. Itis preferred that the distance w between the extending portion 253 andeach of the opposite side surfaces 2162 of the groove portion 216 isabout 1.5 to about 5 times as great as the thickness t of the extendingportion 253. The distance w denotes the shortest distance between thelateral surface of the extending portion 253 and the corresponding sidesurface 2162 of the groove portion 216 opposed to the lateral surface.In the example shown in FIG. 4, the distance w refers to the distanceleading from the border between the side surface 2162 and the bottomsurface 2161 of the groove portion 216 to the border between the lateralsurface of the extending portion 253 and the bottom surface 2161 of thegroove portion 216.

In the spindle motor 1, it is preferred that the distance w is fromabout 0.15 mm to about 1.5 mm and the thickness t is from about 0.1 mmto about 0.3 mm. It is also preferred that the width of the extendingportion 253 of the FPC 25 is from about 1.5 mm to about 3.5 mm, thedepth of the groove portion 216 being from about 0.3 mm to about 0.9 mmand the length of the groove portion 216 being from about 1.7 mm toabout 5.0 mm. Moreover, it is preferred that the diameter of the centralregion 213 is from about 15 mm to about 30 mm. In the present preferredembodiment, the distance w is about 0.3 mm and the thickness t is about0.18 mm. Furthermore, the width of the extending portion 253 of the FPC25 is about 2.54 mm, the depth of the groove portion 216 being about 0.6mm, the length of the groove portion 216 being about 3.0 mm and thediameter of the central region 213 being about 22 mm.

As indicated by hatching lines in FIG. 3, the connection portion 252 ofthe FPC 25 arranged within the recess portion 215 of the base plate 21is covered in its entirety with a resin layer 26. As set forth earlier,the FPC 25 is attached to the lower surface 211 of the base plate 21 byan adhesive agent. Consequently, the connection portion 252 of the FPC25 is fixed in place within the recess portion 215 by the adhesive agentexisting between the connection portion 252 and the bottom surface ofthe recess portion 215 and also by the resin layer 26. The through holes212 pierced in the base plate 21 and the through holes 250 formed in theFPC 25 are blocked by the adhesive agent and the resin layer 26, therebyhermetically sealing the internal space 610 of the housing 61.

When forming the resin layer 26, the base plate 21 is held in avertically inverted state so that the recess portion 215 can be openedupwards along the direction of gravity. In other words, the base plate21 is held to ensure that the axial lower side of the spindle motor 1faces upwards along the direction of gravity. A resin material withflowability is applied on the recess portion 215 in a state that theconnection portion 252 of the FPC 25 is accommodated within the recessportion 215. The resin material with flowability will be referred to asa flowable resin material herein below. Then, the flowable resinmaterial is cured to form the resin layer 26. In the present preferredembodiment, use is made of, e.g., a thermally curable adhesive agent asthe flowable resin material. The resin layer 26 that covers theconnection portion 252 of the FPC 25 is formed by applying the thermallycurable adhesive agent on the recess portion 215 and then heating thesame.

In the spindle motor 1, the height of the resin layer 26 is set smallerthan the depth of the recess portion 215 as can be noted in FIG. 2. Thisprevents the resin layer 26 from protruding downwards beyond the area ofthe central region 213 excluding the recess portion 215 and the grooveportion 216. As a consequence, it becomes possible to reduce thethickness of the spindle motor 1 and the storage disk drive apparatus60.

During the process of forming the resin layer 26, the viscosity of thethermally curable adhesive agent is first decreased by heating beforethe adhesive agent is subjected to curing. Thus the thermally curableadhesive agent flows into the groove portion 216 under the action of acapillary force generated in the groove portion 216. In particular, thethermally curable adhesive agent flows into the groove portion 216 underthe action of a capillary force generated in the space surrounded by theopposite side surfaces 2162 and the bottom surface 2161 of the grooveportion 216 and the lateral surfaces 2531 of the extending portion 253of the FPC 25. In the present preferred embodiment, the viscosity of thethermally curable adhesive agent is from about 0.5 Pa·s to about 13 Pa·swhen the adhesive agent is in the lowest viscous state. As illustratedin FIG. 3, the leading end of the thermally curable adhesive agentflowing into the groove portion 216 is stopped near the middle of thegroove portion 216 before it reaches the boundary between the grooveportion 216 and the peripheral region 214. As the thermally curableadhesive agent is cured to form the resin layer 26, a portion of theextending portion 253 of the FPC 25 (namely, the portion of theextending portion 253 adjacent to the connection portion 252) is coveredwith the resin layer 26 in the groove portion 216 and fixed in placewithin the groove portion 216. This improves the bonding force betweenthe FPC 25 and the base plate 21 and prevents the FPC 25 from beingseparated from the base plate 21.

Now, it is assumed that there exists a spindle motor in which theopposite side surfaces of the groove portion of the base plate areperpendicular or substantially perpendicular to the bottom surface ofthe groove portion, with the width of the groove portion beingsubstantially constant in the radial direction. Below, such a spindlemotor will be referred to as a comparative spindle motor. In case of thecomparative spindle motor, a strong capillary force is generated in thegroove portion. Therefore, there is a possibility that a large quantityof thermally curable adhesive agent will flow into the groove portionand then overflow toward the peripheral region during the course offorming the resin layer. If the thermally curable adhesive agent flowingout of the groove portion flows down along the slanting area of theperipheral region positioned nearer to the rotor unit than is thecentral region and eventually reaches the external terminal portion ofthe FPC arranged in the horizontal area, the terminals arranged forconnection with external devices may possibly be covered with theadhesive agent, thus leading to a connection defect.

In the spindle motor 1 of the first preferred embodiment, however, theopposite side surfaces 2162 gradually sloping downwards in the directionof the central axis J1 as they go away from the bottom surface 2161 inthe circumferential direction are arranged at the circumferentiallyopposite sides of the bottom surface 2161 of the groove portion 216.This construction helps suppress the generation of a capillary force inthe groove portion 216. As a result, it is possible to prevent thethermally curable adhesive agent from flowing out to the peripheralregion 214 through the groove portion 216 when the adhesive agent isapplied on the recess portion 215 defined on the lower surface 211 ofthe base plate 21 of the spindle motor 1.

In the groove portion 216, the angle θ1 between the bottom surface 2161and each of the opposite side surfaces 2162 is set equal to or greaterthan approximately 95°. This construction makes it possible to morereliably suppress that generation of a capillary force in the grooveportion 216 than when the angle θ1 is smaller than approximately 95°.Furthermore, the thermally curable adhesive agent is more reliablyprevented from flowing out to the peripheral region 214 through thegroove portion 216. Further, the angle θ1 between the bottom surface2161 and each of the opposite side surfaces 2162 is set equal to orsmaller than approximately 175°. This construction helps prevent themaximum width of the groove portion 216 from becoming unnecessarilygreater. The term “maximum width” refers to the width between theopposite side surfaces 2162 of the groove portion 216 at the oppositeside from the bottom surface 2161. As a result, it is possible toprevent the extending portion 253 of the FPC 25 accommodated in thegroove portion 216 from making contact with external objects andeventually suffering from damage.

In the spindle motor 1, the distance w between the extending portion 253of the FPC 25 and the opposite side surfaces 2162 of the groove portion216 is set at least about 1.5 times greater than the thickness t of theextending portion 253. This construction helps suppress generation of acapillary force in between the extending portion 253 and the oppositeside surfaces 2162 of the groove portion 216. This makes it possible toprevent the thermally curable adhesive agent from flowing out to theperipheral region 214 through between the extending portion 253 and theopposite side surfaces 2162 of the groove portion 216. The distance wbetween the extending portion 253 of the FPC 25 and the opposite sidesurfaces 2162 of the groove portion 216 is set at most about 5 timesgreater than the thickness t of the extending portion 253. Thisconstruction prevents the maximum width of the groove portion 216 fromunnecessarily becoming greater. As a result, it is possible to morereliably prevent the extending portion 253 from making contact withexternal objects and eventually suffering from damage during the processof fabricating the storage disk drive apparatus 60 or other situations.

As described above, it is possible in the spindle motor 1 to prevent thethermally curable adhesive agent from flowing into the peripheral region214 through the groove portion 216 when the adhesive agent is applied onthe recess portion 215 of the base plate 21. For the very reason, theperipheral region 214 is positioned higher than the groove portion 216in the spindle motor 1. This construction is particularly suitable foruse in a spindle motor having a structure in which a thermally curableadhesive agent is likely to spread over a peripheral region when itflows out of a groove portion.

In the groove portion 216, it is preferred that the opposite sidesurfaces 2162 slope downwards as they go away from the bottom surface2161. However, the present invention is not limited thereto. Forexample, depending on the shape of the FPC 25 or the position and theshape of the application region of the thermally curable adhesive agent,one of the opposite side surfaces 2162 may slope downwards as it extendsaway from the bottom surface 2161 and the other may be generallyperpendicular to the bottom surface 2161. Also in this case, it ispossible to suppress generation of a capillary force in the grooveportion 216 and also to prevent the thermally curable adhesive agentfrom flowing out to the peripheral region 214 through the groove portion216. The capillary force generated in the groove portion 216 refers tothe capillary force that would otherwise be generated in the spacesurrounded by the bottom surface 2161 and one inclined side surface 2162of the groove portion 216 and one lateral surface 2531 of the extendingportion 253 of the FPC 25.

Next, description will be made on a spindle motor in accordance with amodified example of the first preferred embodiment of the presentinvention. FIG. 5A is a partial section view showing the base plate 21of a spindle motor 1 a in accordance with a modified example of thefirst preferred embodiment. FIG. 5A corresponds to FIG. 4 showing thespindle motor 1 in accordance with the first preferred embodiment.Referring to FIG. 5A, a groove portion 216 a differing in shape from thegroove portion 216 shown in FIGS. 3 and 4 is defined on the lowersurface 211 of the base plate 21 in the spindle motor 1 a. Otherstructures remain the same as the structures of the spindle motor 1shown in FIGS. 2 and 3. In the following description, the equivalentcomponents will be designated by like reference numerals.

As shown in FIG. 5A, the groove portion 216 a that interconnects therecess portion 215 of the central region 213 and the peripheral region214 (see FIGS. 2 and 3) is defined on the lower surface 211 of the baseplate 21. Each of the opposite side surfaces 2162 of the groove portion216 a is provided with a slant surface 2162 a and a side wall 2162 b.The slant surface 2162 a is defined by a planar surface graduallysloping downwards as it extends away from the bottom surface 2161 in thecircumferential direction about the central axis J1. The side wall 2162b is defined by a planar surface extending from the lower portion of theslant surface 2162 a to the lower edge 2168 of the groove portion 216.The angle between the slant surface 2162 a and the bottom surface 2161of the groove portion 216 a is from approximately 95° to approximately175°. The side wall 2162 b is perpendicular or substantiallyperpendicular to the bottom surface 2161.

In the spindle motor 1 a of the modified example of the first preferredembodiment described above, the slant surface 2162 a gradually slopingdownwards as it extends away from the bottom surface 2161 in thecircumferential direction is defined at each of the circumferentiallyopposite sides of the bottom surface 2161 of the groove portion 216 a.As is the case in the first preferred embodiment, this constructionhelps suppress the generation of a capillary force in the groove portion216 a. Consequently, it is possible to prevent the thermally curableadhesive agent from flowing out into the peripheral region 214 throughthe groove portion 216 a.

Alternatively, the side wall 2162 b of the groove portion 216 a may bedefined by a surface inclined with respect to the bottom surface 2161.It is preferred that the slant surface 2162 a is arranged at theopposite sides of the bottom surface 2161 in the groove portion 216 a.However, the slant surface 2162 a may be arranged at only onecircumferential side of the bottom surface 2161 between the bottomsurface 2161 and the side wall 2162 b. The bottom surface 2161 and theside wall 2162 b may be directly connected to each other at the othercircumferential side of the bottom surface 2161. Also in this case, itis possible to suppress generation of a capillary force at the side ofthe groove portion 216 where the slant surface 2162 a is arranged. Thismakes it possible to prevent the thermally curable adhesive agent fromflowing out to the peripheral region 214 through the groove portion 216a.

FIG. 5B is a partial section view of the base plate 21 illustrating amodified example of the groove portion 216 a. As shown in FIG. 5B, theopposite slant surfaces 2162 a of the groove portion 216 a arranged atthe opposite sides of the bottom surface 2161 may include curvedsurfaces bulging upwards in the direction of the central axis J1(namely, downwards in FIG. 5B).

Next, description will be made on a spindle motor in accordance with asecond preferred embodiment of the present invention. FIG. 6 is anenlarged bottom view showing the portion of the stator unit 2 around thecentral axis J1 in a spindle motor 1 b of the second preferredembodiment. As shown in FIG. 6, a groove portion 216 b different inshape than the groove portion 216 shown in FIG. 3 is defined on thelower surface 211 of the base plate 21 in the spindle motor 1 b. Otherstructures remain the same as the structures of the spindle motor 1shown in FIGS. 2 and 3. In the following description, the equivalentcomponents will be designated by like reference numerals.

FIG. 7 is a enlarged bottom view showing the recess portion 215 and itssurroundings in the spindle motor 1 b. For the purpose of furtheringeasier understanding, the resin layer 26 is omitted from FIGS. 7, 8A,8B, 9, and 11. As shown in FIG. 7, a groove portion 216 b is defined onthe lower surface 211 of the base plate 21 to interconnect the recessportion 215 of the central region 213 and the peripheral region 214.Each of the opposite side surfaces 2162 of the groove portion 216 b isgenerally perpendicular to the lower surface 2161 of the groove portion216 b. The width of the groove portion 216 b is gradually decreasedtoward the central axis J1 over substantially the full radial length ofthe groove portion 216 b. In this regard, the width of the grooveportion 216 b refers to the distance between the opposite side surfaces2162 in a direction perpendicular or substantially perpendicular to theradial direction. In other words, the distance between the opposite sidesurfaces 2162 of the groove portion 216 b is gradually reduced oversubstantially the entire length of the groove portion 216 b from theradial outer end portion to the radial inner end portion. The term “fulllength” denotes the total length of the groove portion 216 b excludingthe chamfered regions of the radial inner and outer end portions.

The opposite side surfaces 2162 of the groove portion 216 b arepreferably finely chamfered near the boundary between the recess portion215 and the groove portion 216 b and near the boundary 2163 between thegroove portion 216 b and the peripheral region 214. The portions of theopposite side surfaces 2162 other than the portions near theafore-mentioned two boundaries, i.e., the portions of the opposite sidesurfaces 2162 lying between the chamfered regions near the twoboundaries, extend generally rectilinearly when seen in a plan view. Inthe following description, the portions of the opposite side surfaces2162 extending generally rectilinearly when seen in a plan view will bereferred to as “planar portions 2164”.

Within the groove portion 216 b, the opposite lateral surfaces 2531 ofthe extending portion 253 of the FPC 25 are formed to extend generallyparallel to the center line 2165 of the groove portion 216 b. The centerline 2165 refers to an imaginary line extending radially from thecentral axis J1 to pass through the middle point of the width of thegroove portion 216 b. When seen in a plan view, the angle θ2 between theplanar portion 2164 of each side surface 2162 of the groove portion 216b and the corresponding lateral surface 2531 of the extending portion253 opposed to the side surface 2162 is preferably equal to or greaterthan approximately 10° and smaller than approximately 90°, and morepreferably from approximately 10° to approximately 80°. In the presentpreferred embodiment, the angle θ2 is set equal to approximately 45°.

Referring to FIG. 6, the connection portion 252 of the FPC 25 isaccommodated within the recess portion 215 of the base plate 21 as isthe case in the first preferred embodiment. The connection portion 252is attached to the base plate 21 by an adhesive agent existing betweenitself and the bottom surface of the recess portion 215. A thermallycurable adhesive agent is applied on the recess portion 215 and is curedto form a resin layer 26 that covers the connection portion 252 of theFPC 25 in its entirety.

In the course of forming the resin layer 26, the thermally curableadhesive agent is allowed to flow into the groove portion 216 b from therecess portion 215 and is cured in a state that it has arrived near thecenter of the groove portion 216 b. As a result, a portion of theextending portion 253 of the FPC 25 (namely, the portion of theextending portion 253 adjacent to the connection portion 252) is coveredwith the resin layer 26 and fixed in place within the groove portion 216b. This arrangement improves the bonding force between the FPC 25 andthe base plate 21 and prevents the FPC 25 from being separated from thebase plate 21.

In the spindle motor 1 b of the second preferred embodiment, thedistance between the opposite side surfaces 2162 of the groove portion216 b when seen in a plan view is gradually decreased over substantiallythe entire length of the groove portion 216 b from the radial outer endportion to the radial inner end portion. Therefore, a surface tensionacts on the thermally curable adhesive agent in between the oppositeside surfaces 2162 of the groove portion 216 b and the opposite lateralsurfaces 2531 of the extending portion 253. Consequently, it is possibleto prevent the thermally curable adhesive agent from flowing out to theperipheral region 214 through the groove portion 216 b when the adhesiveagent is applied on the recess portion 215 defined on the lower surface211 of the base plate 21 of the spindle motor 1 b.

When seen in a plan view, the angle θ2 between the planar portion 2164of each side surface 2162 of the groove portion 216 b and thecorresponding lateral surface 2531 of the extending portion 253 is setequal to or greater than approximately 10°. This makes it possible tosufficiently increase the width of the groove portion 216 b toward theperipheral region 214, thereby further suppressing generation of acapillary force in the groove portion 216 b. Furthermore, the angle θ2is set smaller than approximately 90° (and preferably equal to orsmaller than approximately 80°). This prevents the width of the grooveportion 216 b from becoming unnecessarily larger. As a result, it ispossible to more reliably prevent the extending portion 253 of the FPC25 accommodated in the groove portion 216 b from making contact withexternal objects and eventually suffering from damage.

Referring to FIG. 8A, instead of the planar portion 2164, a curvedsurface portion 2164 a having a curvilinear shape bulging toward thecenter line 2165 of the groove portion 216 b when seen in a plan viewmay be arranged in each of the opposite side surfaces 2162 of the grooveportion 216 b. In this case, the distance between the opposite sidesurfaces 2162 of the groove portion 216 b is gradually decreased oversubstantially the entire length of the groove portion 216 b from theradial outer end portion to the radial inner end portion. This makes itpossible to prevent the thermally curable adhesive agent from flowingout to the peripheral region 214 through the groove portion 216 b.

When the curved surface portion 2164 a is arranged in each of theopposite side surfaces 2162 of the groove portion 216 b as set forthabove, the plan-view average angle between the curved surface portion2164 a of each of the opposite side surfaces 2162 and the correspondinglateral surface 2531 of the extending portion 253 is set equal to orgreater than approximately 10° in the respective side surfaces 2161 ofthe groove portion 216 b. With this arrangement, the thermally curableadhesive agent is more reliably prevented from flowing out to theperipheral region 214. The term “average angle” refers to the radialaverage of the varying angles between the curved surface portion 2164 aand each of the opposite lateral surfaces 2531 of the extending portion253. Furthermore, the average angle is set smaller than approximately90° (and preferably less than or equal to approximately 80°). By doingso, the extending portion 253 of the FPC 25 accommodated within thegroove portion 216 b can be reliably protected from damage.

In the spindle motor 1 b of the second preferred embodiment, it is notalways necessary that the distance between the opposite side surfaces2162 of the groove portion 216 b is gradually decreased oversubstantially the entire length of the groove portion 216 b from theouter end portion to the inner end portion. It may be sufficient if thedistance is gradually decreased over a specified extent from the outerend portion toward the inner end portion. The specified extent may referto, e.g., a range of about 1 mm or more extending from the boundary 2163between the groove portion 216 b and the peripheral region 214 towardthe recess portion 215. For example, as illustrated in FIG. 8B, theopposite side surfaces 2162 of the groove portion 216 may have asemicircular shape bulging toward each of the opposite lateral surfaces2531 of the extending portion 253 when seen in a plan view. Also withthis configuration, it is possible to prevent the thermally curableadhesive agent from flowing out to the peripheral region 214.

Next, description will be made on a spindle motor in accordance with amodified example of the first preferred embodiment of the presentinvention. FIG. 9 is an enlarged bottom view showing the recess portion215 and its neighborhood formed on the lower surface 211 of the baseplate 21 of a spindle motor 1 c in accordance with a modified example ofthe first preferred embodiment. In the spindle motor 1 c shown in FIG.9, a groove portion 216 c differing in shape from the groove portion 216illustrated in FIG. 3 is defined on the lower surface 211 of the baseplate 21. Other structures remain the same as the structures of thespindle motor 1 shown in FIGS. 2 and 3. In the following description,the equivalent components will be designated by like reference numerals.

In the spindle motor 1 c shown in FIG. 9, the plan-view distance betweenthe opposite side surfaces 2162 of the groove portion 216 c is graduallydecreased over substantially the entire length of the groove portion 216c from the radial outer end portion to the radial inner end portion. Theopposite side surfaces 2162 of the groove portion 216 c are preferablyfinely chamfered near the boundary between the recess portion 215 andthe groove portion 216 c and near the boundary 2163 between the grooveportion 216 c and the peripheral region 214.

The portions of the opposite side surfaces 2162 other than the portionsnear the afore-mentioned two boundaries, i.e., the portions of theopposite side surfaces 2162 lying between the chamfered regions near thetwo boundaries, will be referred to as “planar portions 2164”.

FIG. 10 is a partial section view of the base plate 21 taken along lineB-B in FIG. 9. The cross sectional plane shown in FIG. 10 isperpendicular or substantially perpendicular to the planar portion 2164(see FIG. 9) of one side surface 2162 of the groove portion 216 c. Asshown in FIG. 10, the side surface 2162 of the groove portion 216 c isinclined downwards (namely, toward the upper side in FIG. 10) as itextends away from the bottom surface 2161 in the circumferentialdirection. In the cross sectional plane perpendicular or substantiallyperpendicular to the planar portion 2164 of one side surface 2162, theangle θ3 between the bottom surface 2161 and the side surface 2162 ofthe groove portion 216 c is from approximately 95° to approximately 175°as is the case in the first preferred embodiment. Just like the firstpreferred embodiment, this prevents the thermally curable adhesive agentapplied on the recess portion 215 shown in FIG. 9 from flowing out tothe peripheral region 214 through the groove portion 216 c. Furthermore,it is possible to prevent the extending portion 253 of the FPC 25accommodated in the groove portion 216 c from making contact withexternal objects and eventually suffering from damage.

In the groove portion 216 c, the distance between the opposite sidesurfaces 2162 is gradually decreased over substantially the entirelength of the groove portion 216 c from the radial outer end portion tothe radial inner end portion. This makes it possible to reliably preventthe thermally curable adhesive agent from flowing out to the peripheralregion 214 through the groove portion 216 c.

The plan-view angle θ4 between the planar portion 2164 of each of theopposite side surfaces 2162 of the groove portion 216 c and thecorresponding lateral surface 2531 of the extending portion 253 is fromapproximately 10° to less than approximately 90° (and preferably fromapproximately 10° to approximately 80°). This construction more reliablyprevents the thermally curable adhesive agent from flowing out to theperipheral region 214. Furthermore, it is possible to more reliablyprevent the extending portion 253 of the FPC 25 from making contact withexternal objects and eventually suffering from damage.

In the spindle motor 1 c, each of the opposite side surfaces 2162 of thegroove portion 216 c may be provided with, instead of the planar portion2164, a curved surface portion bulging toward the extending portion 253.In this case, the distance between the opposite side surfaces 2162 ofthe groove portion 216 c is gradually decreased over substantially theentire length of the groove portion 216 c from the radial outer endportion to the radial inner end portion. This construction makes itpossible to more reliably prevent the thermally curable adhesive agentfrom flowing out to the peripheral region 214 through the groove portion216 c. The plan-view average angle between the curved surface portion ofeach of the opposite side surfaces 2162 of the groove portion 216 c andthe corresponding lateral surface 2531 of the extending portion 253 isfrom approximately 10° to less than approximately 90° (and preferablyfrom approximately 10° to approximately 80°). With this construction, itis possible to more reliably prevent the thermally curable adhesiveagent from flowing out to the peripheral region 214 and also to morereliably protect the extending portion 253 of the FPC 25 from damage.

In the spindle motor 1 c, it is not always necessary that the distancebetween the opposite side surfaces 2162 of the groove portion 216 c isgradually decreased over substantially the entire length of the grooveportion 216 c from the outer end portion to the inner end portion. Forexample, it may be sufficient if the distance is gradually decreasedover a specified distance from the outer end portion toward the innerend portion. This configuration makes it possible to prevent thethermally curable adhesive agent from flowing out to the peripheralregion 214. The specified distance may refer to, e.g., a range of about1 mm or more extending from the boundary 2163 between the groove portion216 c and the peripheral region 214 toward the recess portion 215.

Next, description will be made on a spindle motor in accordance withanother modified example of the first preferred embodiment of thepresent invention. FIG. 11 is an enlarged bottom view showing the recessportion 215 and its neighborhood formed on the lower surface 211 of thebase plate 21 of a spindle motor 1 d in accordance with another modifiedexample of the first preferred embodiment. In the spindle motor 1 dshown in FIG. 11, a groove portion 216 d differing in shape from thegroove portion 216 illustrated in FIG. 3 is defined on the lower surface211 of the base plate 21. Other structures remain the same as thestructures of the spindle motor 1 shown in FIGS. 2 and 3. In thefollowing description, the equivalent components will be designated bylike reference numerals.

As shown in FIG. 11, the width of the groove portion 216 d, i.e., thewidth of the groove portion 216 d in a direction perpendicular orsubstantially perpendicular to the radial direction, is substantiallyconstant along the radial direction. Each of the opposite side surfaces2162 of the groove portion 216 d is perpendicular or substantiallyperpendicular to the bottom surface 2161 of the groove portion 216 d.

FIG. 12 is a partial section view of the base plate 21 taken along lineC-C in FIG. 11. For the purpose of facilitating easier understanding, aportion of the component lying behind the cross-sectional plane isillustrated with a broken line (this also holds true in FIG. 13). In thespindle motor 1 d shown in FIGS. 11 and 12, the bottom surface 2161 ofthe groove portion 216 d has a trench portion 2166 indented upward fromthe bottom surface 2161. The upper side from the bottom surface 2161denotes the side at which the rotor unit 3 lies, i.e., the lower side inFIG. 12. With this construction, the thermally curable adhesive agent(the hatched portion in FIG. 12) flowing into the groove portion 216 dfrom the recess portion 215 is stopped in the trench portion 2166 duringthe course of applying the adhesive agent on the recess portion 215. Asa result, it is possible to prevent the thermally curable adhesive agentfrom flowing out to the peripheral region 214 through the groove portion216 d.

As can be seen in FIG. 11, the trench portion 2166 extends continuouslyfrom one of the opposite side surfaces 2162 of the groove portion 216 dto the other. This ensures that the thermally curable adhesive agentflowing into the groove portion 216 d is stopped in the trench portion2166. Consequently, it is possible to more reliably prevent thethermally curable adhesive agent from flowing out to the peripheralregion 214 through the groove portion 216 d.

Next, description will be made on a spindle motor in accordance with afurther modified example of the first preferred embodiment of thepresent invention. FIG. 13 is a section view showing a portion of thebase plate 21 of a spindle motor 1 e in accordance with a furthermodified example of the first preferred embodiment, which viewcorresponds to FIG. 12. In the spindle motor 1 e shown in FIG. 13, thebottom surface 2161 of the groove portion 216 e is provided with aprotrusion portion 2167 protruding downwards, i.e., upwards in FIG. 13away from the rotor unit 3. Other structures remain the same as thestructures of the spindle motor 1 d shown in FIG. 11. In the followingdescription, the equivalent components will be designated by likereference numerals.

In the spindle motor 1 e, the thermally curable adhesive agent (hatchedin FIG. 13) flowing into the groove portion 216 e from the recessportion 215 is dammed by the protrusion portion 2167 during the processof applying the thermally curable adhesive agent on the recess portion215. This prevents the adhesive agent from flowing out to the peripheralregion 214 through the groove portion 216 e. As can be seen in FIG. 13,the protrusion portion 2167 has a height smaller than that of thecentral region 213 when measured from the bottom surface 2161 of thegroove portion 216 e. The tip end of the protrusion portion 2167 doesnot protrude downwards in the direction of the central axis J1 (namely,upwards in FIG. 13) beyond the central region 213.

Similarly, the extending portion 253 of the FPC 25 making contact withthe tip end of the protrusion portion 2167 does not protrude downwardsbeyond the central region 213. This assists in avoiding an increase inthe thickness of the spindle motor 1 e.

In the groove portion 216 e, the protrusion portion 2167 extendscontinuously from one of the opposite side surfaces 2162 of the grooveportion 216 e to the other (see FIG. 11). This makes it possible for theprotrusion portion 2167 to more reliably dam up the thermally curableadhesive agent flowing into the groove portion 216 e. As a result, it ispossible to more reliably prevent the adhesive agent from flowing out tothe peripheral region 214 through the groove portion 216 e.

It is not always necessary that the trench portion 2166 shown in FIGS.11 and 12 extends continuously from one of the opposite side surfaces2162 of the groove portion 216 d to the other. It may be sufficient ifthe trench portion 2166 is formed in the regions between the oppositeside surfaces 2162 of the groove portion 216 d and the opposite lateralsurfaces 2531 of the extending portion 253 of the FPC 25. This makes itpossible to prevent the adhesive agent from flowing out to theperipheral region 214 through the groove portion 216 d. The regionsbetween the opposite side surfaces 2162 of the groove portion 216 d andthe opposite lateral surfaces 2531 of the extending portion 253 of theFPC 25 refer to the two regions on the bottom surface 2161 of the grooveportion 216 d between the opposite side surfaces 2162 and the oppositelateral surfaces 2531 that oppose each other.

Furthermore, it is not always necessary that the protrusion portion 2167shown in FIG. 13 extend continuously from one of the opposite sidesurfaces 2162 of the groove portion 216 e (see FIG. 11) to the other.For example, it may be sufficient if the protrusion portion 2167 isdefined in the regions between the opposite side surfaces 2162 of thegroove portion 216 e and the opposite lateral surfaces 2531 of theextending portion 253 of the FPC 25. This makes it possible to preventthe adhesive agent from flowing out to the peripheral region 214 throughthe groove portion 216 e.

While certain preferred embodiments of the present invention and theirmodified examples have been described hereinabove, the present inventionis not limited thereto but may be modified in many different ways.

The task of fixing the connection portion 252 of the FPC 25 within therecess portion 215 may be realized, e.g., only by the resin layer 26that covers the entirety of the connection portion 252. In this case,the through holes 212 and 250 pierced through the base plate 21 and theFPC 25 are blocked by the resin layer 26, thus hermetically sealing theinternal space 610 of the housing 61. Alternatively, the connectionportion 252 may be fixed within the recess portion 215 only or mainlythrough the adhesive agent existing between the connection portion 252and the bottom surface of the recess portion 215. In this case, theresin layer 26 that covers the connection portion 252 is arranged atleast in the region extending from the electrodes 255, at which theconnection portion 252 is connected to the stator 24, to the boundarybetween the recess portion 215 and the groove portion of the base plate21. The internal space 610 of the housing 61 is hermetically sealed bythis construction.

In the spindle motors described above, the resin layer 26 may be formedby applying, e.g., an ultraviolet-curable adhesive agent as the flowableresin material on the recess portion 215. In this case, the viscosity ofthe ultraviolet-curable adhesive agent is first reduced by theirradiation of ultraviolet rays, after which the adhesive agent iscured. In the spindle motors described above, however, it is possible toprevent the ultraviolet-curable adhesive agent from flowing out to theperipheral region 214 through the groove portion. The structures of thespindle motors that can prevent outflow of the flowable resin materialin this way are particularly useful in case where the thermally curableadhesive agent or the ultraviolet-curable adhesive agent whose viscosityis first reduced prior to its curing is applied on the recess portion215. In the spindle motors described above, the thermally curableadhesive agent and the ultraviolet-curable adhesive agent may be used incombination. Alternatively, other resin materials may also be used inplace of the thermally curable adhesive agent and theultraviolet-curable adhesive agent.

In the spindle motors described above, a rigid printed circuit boardinstead of the FPC 25 may be attached to the lower surface 211 of thebase plate 21. In this case, the task of fixing the rigid printedcircuit board to the base plate 21 may be performed, e.g., by fittingjuts of the rigid printed circuit board to attachment holes of the baseplate 21 without having to apply an adhesive agent to between the lowersurface 211 of the base plate 21 and the rigid printed circuit board.The printed circuit board mentioned herein includes a so-called circuitboard that incorporates wiring lines, chips and the like arranged on aboard.

It is not always necessary that the peripheral region 214 defined on thelower surface 211 of the base plate 21 lies higher than the grooveportion in the direction of the central axis J1. For example, it may besufficient if the peripheral region 214 lies higher than the centralregion 213, i.e., the lowermost surface region of the lower surface 211of the base plate 21 in which the recess portion 215 is defined. Theperipheral region 214 may be, e.g., a horizontal surface flush with thebottom surface 2161 of the groove portion.

In the spindle motors of the foregoing preferred embodiments, it is notalways necessary that the base portion arranged to hold the respectiveportions of the stator unit 2 in place is defined of the base plate 21which is a portion of the first housing member 611. For example, thebase portion may be a bracket produced independently of and attached tothe first housing member 611 to form a portion of the housing 61.

Furthermore, it is not always necessary that the spindle motors are ofan outer rotor type in which the rotor magnet 32 is arranged outside thestator 24. The spindle motors may be an inner rotor type in which therotor magnet 32 is arranged inside the stator 24.

The spindle motors described above are suitable for use in a storagedisk drive apparatus incorporating an access unit that performs one orboth of the tasks of reading and writing information with respect to astorage disk, i.e., a reading task and/or a writing task. The storagedisk drive apparatus 60 provided with the spindle motors can be used asan apparatus for driving other disk-shaped storage media such as anoptical disk, a magneto-optical disk and the like, as well as themagnetic disk. The spindle motors may be used in various devices otherthan the storage disk drive apparatus.

FIG. 14 is a bottom view showing yet another modified example of thebase plate 21. FIG. 15 is an enlarged view of the central region 213 ofthe base plate 21. The structure of the base plate 21 according to thepresent modified example is substantially similar to the structure ofthe base plate 21 illustrated in FIGS. 1 to 4 and 13. The base plate 21according to the present modified example is different from the baseplate 21 illustrated in FIG. 4 in that the side surfaces 2162 of thegroove portion 216 preferably are parallel or substantially parallelwith the central axis J1. The base plate 21 according to the presentmodified example is different from the base plate 21 illustrated in FIG.13 in the shape of the protrusion portion 2167. In the other respects,the structure of the base plate 21 according to the present modifiedexample is substantially similar to the structure of the base plate 21illustrated in FIGS. 1 to 4 and 13. As with the structure illustrated inFIG. 13, the protrusion portion 2167 is preferably arranged to extendcontinuously from one of the side surfaces 2162 of the groove portion216 to the other. Note, however, that the protrusion portion 2167 maynot necessarily be arranged to extend continuously from one of the sidesurfaces 2162 to the other, as described above.

The lower surface of the base plate 21 has, at an outer edge portionthereof, attachment reference surfaces 217 used to attach the storagedisk drive apparatus 60 to a predetermined location. The attachmentreference surfaces 217 provided on the lower surface of the base plate21 are preferably four in number, for example. The attachment referencesurfaces 217 are arranged to face downwards. Each of the attachmentreference surfaces 217 includes a screw hole 218 defined therein.

FIG. 16 illustrates a situation in which the flexible printed circuitboard 25 has been attached to the recess portion 215 and the grooveportion 216. Note that, unlike in FIG. 3, a resin layer 26 is notprovided within the recess portion 215. FIG. 17 is a section view of thebase plate 21 and the flexible printed circuit board 25 taken along lineD-D in FIG. 15. The upper side of FIG. 17 corresponds to a lower side ofthe motor 1 in a direction parallel or substantially parallel to thecentral axis J1, i.e., the side on which the stator unit 2 is positionedin the motor 1. Therefore, the protrusion portion 2167 is arranged toprotrude downwards

The shape of a vertical cross-section of the protrusion portion 2167taken along a direction parallel or substantially parallel to thedirection of the extension of the groove portion 216, i.e., taken alongline D-D in FIG. 15, preferably is a trapezoid or a substantialtrapezoid, for example. Alternatively, as illustrated in FIG. 13, theshape of the vertical cross-section of the protrusion portion 2167 mayinclude the shape of an arc or a substantial arc. When the verticalcross-section of the protrusion portion 2167 is in any of these shapes,smooth attachment of the flexible printed circuit board 25 (i.e., anexample circuit board) along the protrusion portion 2167 is easilyachieved. Moreover, this contributes to preventing the flexible printedcircuit board 25 from being separated from the base plate 21, and/orpreventing a gap from being formed between the flexible printed circuitboard 25 and the base plate 21, thereby ensuring that an interior of thestorage disk drive apparatus 60 can remain airtight. Furthermore,referring to FIG. 16, the protrusion portion 2167 is arranged to extendsubstantially perpendicularly to the direction of the extension of theextending portion 253 of the flexible printed circuit board 25. Thiscontributes to preventing the extending portion 253 from deviating fromits intended path in the circumferential direction when the extendingportion 253 passes over the protrusion portion 2167.

In FIG. 17, the level of the attachment reference surfaces 217 and thelevel of the central region 213 are denoted by reference numerals “217”and “213”, respectively. With respect to the direction parallel orsubstantially parallel to the central axis J1, the position of a top ofthe protrusion portion 2167 is preferably at a level lower, in FIG. 17,than that of the attachment reference surfaces 217 by the thickness ofthe flexible printed circuit board 25 or more. The lower side of FIG. 17corresponds to the upper side of the motor 1 when the rotor unit 3 ispositioned upwards. That is, it is preferable that a distance denoted byreference symbol “H1” in FIG. 17 be equal to or greater than thethickness of the flexible printed circuit board 25, to prevent a surfaceof the flexible printed circuit board 25 from being positioned at alevel lower than that of the attachment reference surfaces 217. Thiscontributes to preventing the flexible printed circuit board 25 frominterfering with another component when the storage disk drive apparatus60 is attached to the predetermined location.

More preferably, with respect to the direction parallel or substantiallyparallel to the central axis J1, the position of the top of theprotrusion portion 2167 is at a level lower, in FIG. 17, than that of abottom surface of the central region 213 by the thickness of theflexible printed circuit board 25 or more. The lower side of FIG. 17corresponds to the upper side of the motor 1 when the rotor unit 3 ispositioned upwards. A distance denoted by reference symbol “H2” in FIG.17 is preferably equal to or greater than the thickness of the flexibleprinted circuit board 25. This contributes to preventing the surface ofthe flexible printed circuit board 25 from protruding over the centralregion 213 to interfere with another component. It also contributes tofacilitating an operation of attaching a nameplate to the central region213 so that the nameplate can be attached to the central region quicklyand properly. Furthermore, the position of the top of the protrusionportion 2167 is preferably at a level lower than that of the bottomsurface of the recess portion 215.

FIG. 18 is a bottom view showing the central region 213 when theflowable resin material is supplied to the recess portion 215 to formthe resin layer 26. In FIG. 18, the resin layer 26 is indicated byhatched lines, and a wiring pattern of the flexible printed circuitboard 25 is not shown. When the flowable resin material is applied onthe recess portion 215, the protrusion portion 2167 blocks passage ofthe flowable resin material to prevent an overflow of the flowable resinmaterial, with the result that the resin layer 26 is arranged to spreadalong the flexible printed circuit board 25 until it reaches theprotrusion portion 2167 as illustrated in FIG. 19. The prevention of theoverflow of the flowable resin material is effective when, as in thecase of FIG. 13, the peripheral region 214 is positioned at a levelhigher (i.e., lower in FIG. 19) than that of the groove portion 216 withrespect to the direction parallel or substantially parallel to thecentral axis J1. The flowable resin material is preferably a thermallycurable adhesive agent. Naturally, as mentioned above, the flowableresin material may be an ultraviolet-curable adhesive agent, any ofvarious types of coating agents, or the like. However, any otherflowable resin material could be used if so desired.

In the case where the recess portion 215 and a portion of the grooveportion 216 are covered with the flowable resin material, as in the caseof FIG. 13, it is preferable that the protrusion portion 2167 bearranged to extend at least between each side surface of the extendingportion 253 and both side surfaces 2162 of the groove portion 216. Then,a region within the recess portion 215 which covers at least connectionpoints in the connection portion 252 and extends up to the boundarybetween the recess portion 215 and the groove portion 216 is coveredwith the cured flowable resin material.

The inclusion of the protrusion portion 2167 in the storage disk driveapparatus 60 contributes to improving the rigidity of the base plate 21.This in turn contributes to reducing a vibration of the storage diskdrive apparatus 60, and improving impact resistance thereof. The baseplate 21 provided with the protrusion portion 2167 is especiallysuitable for use in a storage disk drive apparatus with a thickness ofabout 7 mm, for example, which requires the base plate 21 to be thin.

Note that features of the structures as illustrated in FIGS. 1 to 13 andthose of the modified examples thereof as described above with referenceto FIGS. 1 to 13 may be applied to the present modified exampleillustrated in FIGS. 14 to 19 insofar as no contradiction is incurred.For instance, the central region 213 may not necessarily be positionedat a level lower than that of the peripheral region 214.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing the scope andspirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. A spindle motor for use with a storage disk drive apparatus, thespindle motor comprising: a stator unit; and a rotor unit supported tobe rotatable about a central axis with respect to the stator unit;wherein the stator unit includes: a stator arranged around the centralaxis; a base portion including a through hole passing therethrough in adirection parallel or substantially parallel to the central axis, andarranged on a lower side of the rotor unit in the direction parallel orsubstantially parallel to the central axis; and a circuit board attachedto a lower surface of the base portion, and including a connectionportion to which a conductive wire from the stator is connected afterpassing through the through hole, and a strip-shaped extending portionarranged to extend from the connection portion; the lower surface of thebase portion includes: a recess portion arranged to accommodate theconnection portion of the circuit board; and a groove portion arrangedto extend from the recess portion to have the extending portion arrangedtherein; and a bottom surface of the groove portion includes aprotrusion portion arranged to protrude downwards.
 2. The spindle motoraccording to claim 1, wherein the protrusion portion is arranged toextend continuously from one side surface of the groove portion to theother.
 3. The spindle motor according to claim 2, wherein a shape of avertical cross-section of the protrusion portion taken along a directionparallel or substantially parallel to a direction of an extension of thegroove portion includes a trapezoidal shape, a substantially trapezoidalshape, an arc shape, or a substantial arc shape.
 4. The spindle motoraccording to claim 1, wherein the base portion includes an attachmentreference surface arranged to face downwards; and with respect to thedirection parallel or substantially parallel to the central axis, aposition of a top of the protrusion portion is at a level higher thanthat of the attachment reference surface by a distance equal to athickness of the circuit board or more.
 5. The spindle motor accordingto claim 1, wherein the lower surface of the base portion furtherincludes: a central region concentric with the central axis; and aperipheral region arranged radially outward of the central region and ata level higher than that of the central region with respect to thedirection parallel or substantially parallel to the central axis; therecess portion and the groove portion are arranged within the centralregion; and with respect to the direction parallel or substantiallyparallel to the central axis, a position of a top of the protrusionportion is at a level higher than that of a bottom surface of thecentral region by a distance equal to a thickness of the circuit boardor more.
 6. The spindle motor according to claim 1, wherein the lowersurface of the base portion further includes: a central regionconcentric with the central axis; and a peripheral region arrangedradially outward of the central region and at a level higher than thatof the central region with respect to the direction parallel to thecentral axis; the recess portion and the groove portion are arrangedwithin the central region; the protrusion portion is arranged to extendat least between each side surface of the extending portion and bothside surfaces of the groove portion; and a region within the recessportion which covers at least a connection point in the connectionportion and extends up to a boundary between the recess portion and thegroove portion is covered with a cured flowable resin material.
 7. Thespindle motor according to claim 6, wherein the flowable resin materialis arranged to reach the protrusion portion.
 8. The spindle motoraccording to claim 6, wherein the peripheral region is arranged at alevel higher than that of the groove portion with respect to thedirection parallel or substantially parallel to the central axis.
 9. Thespindle motor according to claim 6, wherein the flowable resin materialincludes a thermally curable adhesive agent.
 10. A storage disk driveapparatus comprising: the spindle motor of claim 1 arranged to rotate astorage disk used for information storage; an access unit arranged toread or write information from or to the storage disk; and a housingarranged to contain the spindle motor and the access unit.
 11. Thestorage disk drive apparatus according to claim 10, wherein the storagedisk drive apparatus has a thickness of about 7 mm.